Formwork for concrete walls

ABSTRACT

There is disclosed a building system utilizing steel joists spaced apart by spanner bars which also support rigid panels which act as formwork for the pouring of concrete. The spanner bars and the joists are so arranged to cooperate that the spanner bars may be removed together with the rigid panels after the concrete has been poured, and the spanner bars, the rigid panels and if desired the steel joists may be reused for formwork for additional poured concrete construction. Alternatively the joists may be left in place either with top chords embedded in the poured concrete to provide a composite action, or merely supporting the concrete slab in the conventional fashion. A novel cold rolled sheet steel joist may be advantageously used to form a particularly economical composite system. This steel joist is shaped in an I-beam configuration with an upper top chord bent to have the appearance of the letter Z in cross-section for bonding with the concrete floor.

United States Patent [19] Butts et al.

[ FORMWORK FOR CONCRETE WALLS [75] Inventors: Ernest O. Butts; John S. Hall, both of Ottawa, Ontario, Canada [73] Assignee: Hamhro Structural Systems Limited,

Ottawa, Ontario, Canada 22 Filed: May21,1971 [211 App]. No.: 145,758

Related U.S. Application Data [63] Continuation-impart of Ser. No. 872,017, Oct. 29,

1969, abandoned.

[30] Foreign Application Priority Data Cushman [11] 3,819,143 June 25, 1974 Primary Examiner-J. Spencer Overholser Assistant Examiner--B. D. Tobor Attorney, Agent,

1 [57] ABSTRACT There is disclosed a building system utilizing steel joists spaced apart by spanner bars which also support rigid panels which act as formwork for the pouring of crete has been poured, and the spanner bars, the rigid panels and if desired the steel joists may be reused for formwork for additional poured concrete construction. Alternatively the joists may be left in place either with top chords embedded in the poured concrete to provide a composite action, or merely supporting the concrete slab in the conventional fashion A novel cold rolled sheet steel joist may be advantageously used to form a particularly economical composite system. This steel joist is shaped in an I-beam configuration with an upper top chord bent to have the appearance of the letter Z in cross-section for bonding with the concretefloor.

2 Claims, 19 Drawing Figures or rmiqeshmaatmlhrb PATENTEB JUN25 974 sum 2 or 5 PAIENTEDJUNZSIQH 3.819. 143

' sum u UF 5 A ltorney' F ORMWORK FOR CONCRETE WALLS This application is a continuation-in-part of our copending application Ser. No. 872,017, filed Oct. 29, 1969, now abandoned.

The present application relates to building systems and in particular a building system in which a combination of open web joists, spanner bars and rigid panels are utilized to support a poured concrete floor. In accordance with one form of the invention the spanner bars and rigid panels may be removed after the concrete has set and reutilized. In accordance with a further preferred form of the invention the open web steel joist may also be removed after the concrete has set and reused.

The present application also relates to a composite floor system for use in the design and construction of buildings such as large open span buildings in which a cold rolled sheet steel joist is formed in the shape of an I-beam with an upper chord bent to have the appearance of the letter Z in cross section.

An object of the invention is to provide an economical and strong composite floor system by the use of cold rolled sheet steel members.

A further object of the invention is to provide a floor system which can be adapted to permit efficient and economical erection and disassembly of multiple use formwork material to receive the concrete slab of this composite floor system. This is accomplished, by the use of openings which are cut at regular intervals along the horizontal length of the vertical flange of the cold rolled sheet steel joists into which the ends of the spanner bars which are shaped so that they may, by use of a hammer or similar object, be wedged into this opening. Due to the shape of the openings, the removal of the spanner bars is accomplished by moving the spanner bars in the opposite direction as when they were wedged-in during erection. This latter procedure permits safe and easy removal of firstly the spanner bars and secondly the formwork material. Spanner bars and formwork material can then be reused for the subsequent construction of additional composite floor systems following the teachings of the present invention.

In accordance with the present invention there is provided a building system wherein metal joists are supported in parallel spaced relation, and means are provided for removably supporting rigid panels mounted between and filling the space between adjacent joists, said means comprising at least two bars extending between adjacent joists with the ends of the bars being removably held to the joists.

In the accompanying drawings which illustrate embodiments of the present invention,

FIG. I is a vertical section through a building system pursuant to the present invention;

FIG. 2 is a perspective view partly broken away illustrating formwork pursuant to the present invention;

FIG. 3 is a perspective view similar to FIG. 2 illustrating a slightly modified embodiment of the invention;

FIG. 4 is a perspective view of yet another form of the system pursuant to the present invention;

FIG. 5 is a perspectiveview with the panels removed of yet another form of the invention;

FIG. 6 illustrates a preferred form of elongated slot provided for receiving the end of a spanner bar;

FIG. 7 illustrates a spanner bar adapted for utilization with the elongated slot of FIG. 6;.

FIG. 8 illustrates an alternative embodiment of elongated slot;

FIG. 9 illustrates another fonn of spanner bar;

FIG. 10 illustrates analtemative form of elongated slot intended for utilization with a spanner bar as illustrated in FIG. 9;

FIGS. 11 and 1?. illustrate alternative forms of top chord for the open web steel joist for utilization with the roll bar illustrated in FIG. 13;

FIG. 13 illustrates a roll bar adapted for utilization with the top chords of FIGS. 11 and 12;

FIG. 14 is a vertical section through a wall form constructed pursuant to the present invention;

FIG. 15 is a perspective view of one face of a wall form pursuant to the present invention;

FIG. 16 is a perspective view of a cold rolled sheet steel joist in accordance with a preferred form of the invention;

FIG. 17 is a vertical section through the composite floor systems using the applicants novel cold rolled steel joists;

FIG. 18 is a vertical section illustrating the spanner bar and novel cold rolled sheet steel joist; and,

FIG. l9is a plan view of a spanner bar in accordance with a preferred embodiment of the invention.

Referring to FIG. 1 there is shown a vertical section through a building construction utilizing the system of the present invention. Asillustrated, there is shown a concrete wall 10 which may be either poured, masonry, block or could alternatively be a column placed ahead of the floor system. On either side of the wall 10 are placed temporary scaffolds 11 and 12, on the top ends of which are supported open web steel joists or bar joists l3 and 14. Supported between successive open web joists are rigid panels, for example of plywood, l5 and 16. These panels 15 and 16 are supported by a plurality of spanner bars 17 positioned transversely to the joists 13 and 14, the ends of the spanner bars being received in openings 18 formed in the lower edge of the top chord or in the upper part of the web of the open web joists l4 and 15. j

The steps in the process of erecting a building utilizing the building system of the present invention typically would consist of pouring a floor or foundation, erecting vertical walls or columns, positioning temporary scaffolding to support the open web joists, inserting spanner bars and plywood panels between the joists, and pouring the successive floor of the building. After an appropriate period of time, for example seven days, the spanner bars and panels would be stripped from the open web joists, and after a further period of time, for example 28 days, the open web joists would be removed, together with the temporary scaffolding. This material could then be raised to a higher floor of the building and reused to make formwork for pouring a succeeding upper floor of the building.

It should be noted that no requirement for reshoring of the poured concrete floors is raised by the system of the present invention. By allowing the open web joists to remain in place, the necessity for reshoring is avoided, and thus the construction of the building can be accelerated since mechanical trades can have access to the floor at an earlier date than would be required if reshoring were utilized.

As an alternative form of construction it is within the scope of the present invention to support the open web joists on permanent supports in the building structure, and to incorporate the open web joists as permanent portions of the building. Such open web joists may ei ther have a conventional top chord having a flat upper surface, or may utilize a form of top chord provided with shear connection to the concrete to give a composite action which results in a significant decrease in the cost of building construction. It will be appreciated that any poured concrete structure will of course have to include reinforcing elements to strengthen the concrete at critical locations, but for the sake of simplicity such reinforcement has not been illustrated in the drawings of the present invention.

With the system of the present invention it is possible to utilize standard material sizes to form the plywood panels and the spacing of the open web joists may for example be advantageously fixed at approximately 4 foot centers, thereby enabling the use of standard 4 X 8 sheets of plywood which are the most inexpensive size commercially available. It should also be recognized that in accordance with contemporary construction practice, such plywood panels would be treated with a release coating, such as oil, to avoid adherence of the concrete to the panel. Such a release coating enables the ready stripping of the forms from beneath the poured concrete floor with a minimum loss of formwork due to accidental destruction.

As illustrated in FIG. 1, and in other sheets of the drawings, the roll bars 17 may be equipped with the permanent handles 19, or alternatively such roll bars may be utilized together with removable handles resembling spanner wrenches which are utilized to grasp the roll bar for rotation during insertion and removal. As will be discussed hereinbelow, the roll bars are formed of a material of a substantially rectangular cross section and are suitably notched at the ends to stabilize the positioning of the open web joists during construction. Additionally, the plywood panels utilized together with the roll bars serve to give a diaphragm action to reinforce the formwork against horizontal loads during pouring of the concrete floors.

In FIG. 2 there is illustrated in perspective a section of building system pursuant to the present invention as illustrated in FIG. 1. The open web joist 13 supports a spanner bar or roll bar 17 on which a rigid plywood panel 15 is positioned. A like panel 15A is positioned on the opposite side of the open web joist 13 from the panel 15 and is supported by a spanner bar (not illustrated). The form of open web joist shown in FIG. 2 utilizes a hat" section top chord which has a substantially flat upper surface 20 and horizontally extending flanges 21 and 22 to support the edges of the plywood forms 15A and 15 respectively. A portion of an elongated opening 18 is also illustrated in the drawing.

FIG. 3 illustrates an alternative form of top chord which is provided with a flat upper surface 23 with one long vertical leg 24 and a short vertical leg 25. As before, the long vertical leg is provided with elongated openings 18 for cooperation with the roll bars.

FIG. 4 illustrates an alternative embodiment of the invention utilizing an alternative form of top chord for each of the open web joists 13 and in which a second roll bar is utilized to connect the bottom chords of the open web joists 13 to provide bridging where necessary for strengthening the formwork. As before, the plywood panel 15 is supported by the upper roll bar 17 and fits between the joists l3 and has its upper surface substantially flush with the tops of the top chords of the joists 13. It will be noted that the form of top chord illustrated in FIG. 4 includes an upwardly extending channel positioned at either side of the joist into which the ends of the roll bars 17 are fitted. This channel is provided with notches at appropriate locations so that the roll bars may be removed after pouring of the concrete floor.

FIG. 5 illustrates another alternative embodiment of the invention in which the top chord is formed in the shape of an inverted channel with elongated openings for cooperation with the ends of the roll bars, and a bridging bar 25 is provided connecting the bottom chord of the open web joist which bottom chord is formed by a pair of angles with a space therebetween.

FIG. 6 illustrates one form of elongated opening 18 formed in the side of the joist for supporting of the spanner bar.

FIG. 7 illustrates a preferred form of spanner or roll bar formed of rectangular cross sectionmaterial with a notch 26 in each end of the bar 17. In use the bar is turned so that the flat side of the material extends in the long direction of the hole 18 so that the bar may then be inserted in the hole and rotated so that the sides of the notch 26 engage the short edges of the hole 18 to fix the bar in relation to the hole 18.

While FIG. 6 illustrates a preferred form of elongated hole 18, in many cases a hole 18 as illustrated in FIG. 8 would be suitable for use within the present invention. In such case a roll bar 17 as illustrated in FIG. 9 may be utilized for supporting the rigid panels.

FIG. 10 illustrates yet another form of elongated opening which might be utilized with the present invention in which a portion of the material adjacent the opening 27 may be removed as a knockout panel to assist in removal of the spanner bar during stripping of the formwork.

FIG. 11 illustrates a form of top chord which might be utilized with spanner bars of shape illustrated in FIG. 13. In this case the notches 26 are formed in the lower edge of the spanner bar and sit on the upturned lips 28 of the top chord of the open web joist.

FIG. 12 illustrates a shape of top chord shown in FIG. 4 which is also provided with upturned lips 28 to cooperate with a spanner bar such as that illustrated in FIG. 13.

FIG. 14 illustrates the application of the principles of the present invention to erect formwork for vertical constructions such as the pouring of concrete walls. FIG. 15 is a perspective of one side of the formwork illustrated in FIG. 14, and the two figures of drawings will be described together for simplicity. A vertically extending member 50 which resembles an open web joist of tapering depth is positioned vertically and provided with a channel 51 with a plurality of elongated openings 52. Spanner or roll bars 53 are inserted in the openings 52 in the channel 51 and serve to support rigid panels 54 from outward motion. A bottom tie consisting of a pipe spacer 56 is provided at the base of the wallform and a top tie 56 is positioned at the top of the wallfonn. As before the concrete wall is poured the shape being retained by the formwork and after the concrete has set the formwork is stripped by removal of the spanner bars and the panels and subsequently by removal of the vertical reinforcing members 50.

Referring to FIG. 16, there is shown in perspective a cold rolled sheet steel joist constructed in accordance with the present invention. The joist is indicated generally at 110 and consists of a bottom chord 111 in a generally rectangular shape, a vertical flange 112 and a generally Z-shaped top chord 113. In erecting the composite floor system described in FIGS. 17 and 18, special cold rolled sheet steel joists 1 10, in properly spaced parallel relationship, are supported at opposite ends upon any usual and conventional supports.

Positioned between two such novel joists M0 are spanner bars 114 which have tapered and notched ends 115. The ends 115 cooperate with the openings 110 and are wedged into opening 116 in the vertical flange 112 during erection. The plurality of openings 116 are generally rectangular in shape with one side so tapered from the bottom to the top that when spanner bar end 115 is inserted and hammered into the opening 116 spanner bar 114 becomes wedged securely. Supported on the spanner bar 114 is the reusable formwork 119 which is sealed against loss of wet concrete by the return lip of the top chord 113 and the vertical face 112 of the opposite joist 110.

ln accordance with a further feature of the invention, such a shaped spanner bar as seen in FIG. 19 permits the easy installation and removal of spanner bars 114 so that they may be reused. Once the spanner bars are removed the openings 116 serve as pass-ways for electrical and mechanical conduits thereby permitting a saving in the height required between floors.

The top chords 13 of this novel joist may be embedded in the concrete floor 17 which is part of this composite floor system and the reinforcing mesh 18 hangs in a catenary shape between the novel joists 10 to provide a proper reinforcement for the concrete slab. Thus the concrete slab becomes part of the top chord.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In formwork for constructing concrete walls the improvement comprising:

a plurality of tapered, vertically extending open web steel joists each having an inner chord, an outer chord and a tapered open web of serpentine form spacedly joining said chords with said inner chord vertical and said outer chord sloping inwardly from its base to join said inner chord at its top,

said inner chord having a flat inner surface for receiving wall forms and having an outwardly extending flange with a plurality of vertically elongated vertically spaced openings for receiving removable spanner bars to brace said wall forms, each of said spanner bars being an elongated steel bar formed of material having a generally rectangular transverse cross section and having pairs of wide and narrow faces and opposite ends, a notch in a narrow face of said bar adjacent each end thereof, said vertically spaced openings in the outwardly extending flange of said inner chord being shaped to permit entry of an end of a spanner bar therein with the wide faces of said spanner bar vertical, said notches being of a depth sufficient to permit rotation of said spanner bar about a horizontal axis extending longitudinally of the spanner bar, to engage the material of said outwardly extending flange surrounding a vertically extending opening when the spanner bar is rotated to a position with its wide faces horizontal, said spanner bar thereby being locked to said steel joists to maintain the spacing between adjacent joists and to support wall forms positioned adjacent said joists.

2. Formwork as in claim 1 and further including:

a second plurality of tapered, vertically extending open web steel joists like the first plurality in that claim with each joist supporting a plurality of said spanner bars and walls forms as aforesaid and disposed with the respective wall forms spacedly facing each other, and

means bracing the opposite wall forms and joists a predetermined distance apart whereby the space between the wall forms can be filled with concrete.

t: :i: a: i 

1. In formwork for constructing concrete walls the improvement comprising: a plurality of tapered, vertically extending open web steel joists each having an inner chord, an outer chord and a tapered open web of serpentine form spacedly joining said chords with said inner chord vertical and said outer chord sloping inwardly from its base to join said inner chord at its top, said inner chord having a flat inner surface for receiving wall forms and having an outwardly extending flange with a plurality of vertically elongated vertically spaced openings for receiving removable spanner bars to brace said wall forms, each of said spanner bars being an elongated steel bar formed of material having a generally rectangular transverse cross section and having pairs of wide and narrow faces and opposite ends, a notch in a narrow face of said bar adjacent each end thereof, said vertically spaced openings in the outwardly extending flange of said inner chord being shaped to permit entry of an end of a spanner bar therein with the wide faces of said spanner bar vertical, said notches being of a depth sufficient to permit rotation of said spanner bar about a horizontal axis extending longitudinally of the spanner bar, to engage the material of said outwardly extending flange surrounding a vertically extending opening when the spanner bar is rotated to a position with its wide faces horizontal, said spanner bar thereby being locked to said steel joists to maintain the spacing between adjacent joists and to support wall forms positioned adjacent said joists.
 2. Formwork as in claim 1 and further including: a second plurality of tapered, vertically extending open web steel joists like the first plurality in that claim with each joist supporting a plurality of said spanner bars and walls forms as aforesaid and disposed with the respective wall forms spacedly facing each other, and means bracing the opposite wall forms and joists a predetermined distance apart whereby the space between the wall forms can be filled with concrete. 